It has been found under practical conditions that the sealing action of such a lip-type seal, known from DE 3,629,777 C2, is not optimal. Furthermore, the conventional lip-type seal requires a separate carrier strip, countersunk into the board hull, at which the mounting strip with the sealing lip is clamped in place, so that this lip-type seal is relatively expensive in regard to its structure for sailboards that are manufactured in large series.